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Native Clay Glaze


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#1 jrgpots

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Posted 04 March 2014 - 09:38 PM

About 2 months ago I made a terra sig from local clay.  It's a magnesium and iron rich bentonite. In its raw state it is purple and chocolate brown in oxidation. I don't know what it looks like in reduction yet.  It melt at cone 4-5.  I did triaxial blending of Gerstley borate, Nepheline syenite, and the clay with the results below.  The glaze has a satin finish with two coats and semi gloss finish with one coat.  It has a pleasing texture.  I like the tile that has the hole in the test tube.  Lemon juice test showed no discolorations.  There is no crazing.

 

Recipe: Gerstley bborate                6.52

            Neph syenite                     15.22

            local clay/bentonite           78.26

 

It was applied on bone dry clay and single -fired to reduce problems with the high bentonite and its COE.  I think I have my first stable home grown base glaze.

 

What colorants do you think I should try next?  

 

I have thought about adding RIO 6 - 8% to see if it will make a nice satin tenmuko that I could use as the base glase  for a cone 6 oil spot or hares hair glaze.  That is my aspiration.

 

Imput, critique, gut reactions are greatly appreciated.

 

JedAttached File  bentonite glaze.jpg   57.51KB   2 downloads



#2 C. Banks

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Posted 04 March 2014 - 11:06 PM

we fire to ^8-9 but maybe I can offer a couple starting points

80 local clay
15 local calcium (whiting)
5 rio
2 light mgco3

it had an annoying tendency to blister - nothing serious just the odd 3 or 4 blisters every load. it was tolerable but annoying.

I spent some time trying to puzzle them away but gave up after finally figuring out a decent jasper.

there is another black recipe I can share with certainty but unfortunately I'm away from my little black book atm and can't remember the jasper exactly.
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#3 jrgpots

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Posted 04 March 2014 - 11:10 PM

Send it to me if you find it.

Thanks

#4 C. Banks

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Posted 04 March 2014 - 11:30 PM

80 local clay
15 whiting
2 coco3
4 rutile

this matte gold-black came fully functional with next to no fiddling necessary

all amounts are grams
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#5 C. Banks

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Posted 04 March 2014 - 11:33 PM

when I get back home in a couple weeks I'll post the jasper
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#6 C. Banks

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Posted 04 March 2014 - 11:55 PM

the jasper has 10 grams bone ash, black iron oxide, whiting and I pretty sure 10 grams gb as well. the other couple ingredients im unsure of and it adds up to 114 or something

your 'clay' test results sound very familiar

the purplish oil spotting I remember with 10+% of rio was encouraging but I got sidetracked after findings spots of red. iirc 12% rio was the most I tried.
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#7 Wyndham

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Posted 05 March 2014 - 09:28 AM

You might consider 2 glazes, the one you have as the base with more iron 5%, the other the base plus 3134 frit in increments of 10% with about 4-5% rutile for a breaking gloss over the base

Wyndham



#8 jrgpots

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Posted 05 March 2014 - 12:13 PM

You might consider 2 glazes, the one you have as the base with more iron 5%, the other the base plus 3134 frit in increments of 10% with about 4-5% rutile for a breaking gloss over the base
Wyndham

That sounds interesting. I'll be making more test tiles.

Jed

#9 smastca

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Posted 06 March 2014 - 08:06 PM

This is my native clay - a red terra cotta.  Recipe - terra cotta 80; Frit 3134 20.

You can see the little tea dust crystals.

 

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#10 TJR

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Posted 06 March 2014 - 08:16 PM

This is my native clay - a red terra cotta.  Recipe - terra cotta 80; Frit 3134 20.

You can see the little tea dust crystals.

Wow! That's beautiful. Crazing quite a bit though. You could try a line blend of flint-5%.10%15%. To see if you can get a better fit. Of course the frit is also a glass former.

TJR.



#11 C. Banks

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Posted 10 April 2014 - 12:37 PM

here is that jasper

local clay 50
volcanic ash 10
bone ash 10
silica 10
gerstley borate 10
black iron oxide 10
spodumene 10
kona f4 4
mgco3 3

all in grams

nice red breaking black with touches of purple at ^8.5-9 in oxidation
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#12 TJR

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Posted 10 April 2014 - 01:20 PM

O.K.

I had to rewrite your formula so that it looks more like a percentage

local clay  50

volc. ash  10

Flint/silica 10

Ger. Bor.   10

Spodumene10

Total ---------100

Kona f4      4

Mang. carb 3

Black Iron   10

 

So looking at the percentage now, you still have Kona F4 which is a Soda flux. I left it out of the 100% total just for ease of reading the recipe.

If you look at your manganese-you have 3% in the glaze.

You also have a huge amount of black iron.

I would try a line blend without either the manganese or the iron to see what your base looks like.

Then you can add 1% iron, then 2, then 4% etc.

If you were firing in reduction, your glaze would be really dark, and probably run.

Remember, test,test,test, and show us the results.

TJR.



#13 C. Banks

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Posted 13 June 2014 - 01:03 AM

thanks TJR

im online very infrequently and wanted to respond here a few times but this phone tech is ... alien

this is one of my success stories - it only took a few years but after giving up for a year or so I had a thought and threw a hail mary of sorts

the recipe should read magnesium carbonate rather than manganese and is definitely approaching what I would call iron saturated?

it is well behaved at ^9 and, when happy, shows no off browns and much maroon/purple character

if I was to submit a glaze to cm this would be the first one of ? 3
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#14 C. Banks

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Posted 13 June 2014 - 01:18 AM

this may be a fotm (flavour of the month) but it's fun to share an "ooo" moment
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)

#15 jrgpots

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Posted 13 June 2014 - 04:12 PM

Do you have a pic for your latest tweek in the recipe?  I'd love to see it.

 

Jed



#16 C. Banks

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Posted 13 June 2014 - 11:45 PM

It might take a while but I have some images and a few pieces saved that shine up well
"All this of Pot and Potter — Tell me then, Who is the Potter, pray, and who the Pot?" (Omar Khayyam)




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